Hargreaves公式计算宁夏地区参考作物腾发量的研究

Estimation of evapotranspiration in Ningxia by Hargreaves equation

Penman-Monteith公式计算ET0需要大量的气象数据,而这些数据在一些地区尤其是不发达地区缺测情况较多。Hargreaves公式是FAO推荐的在只有气温数据情况下,估算ET0的方法,但在应用时需要对其进行修正。文中利用国家气象数据共享服务网提供的宁夏24个气象站长系列逐旬气象资料(1951-1999年),分别用Penman-Monteith公式,Hargreaves公式计算参考作物腾发量,然后通过回归分析确定出宁夏每一个气象站所代表区域应用Hargreaves公式时的经验系数,提出修正后的Hargreaves计算公式;并用2000-2012年的气象数据对修正后的Hargreaves公式进行验证。结果表明:1)未修正的Hargreaves公式,在宁夏地区的适用性较差,与Penman-Monteith公式计算值对比差异显著。2)修正后的Hargreaves公式计算精度显著提高,与Penman-Monteith公式计算结果有很好的拟合,可见,利用修正后的Hargreaves公式替代PM公式计算宁夏地区参考作物腾发量是可行的。

The Food and Agriculture Organization （FAO） recommends the use of the Penman - Monteith equation for estimating reference evapotranspiration （ET0 ）. However, it requires several measurements of climatic variables; unfortunately, there are a limited number of meteorological stations in many regions to completely collect these climatic variables. When air temperature is the only available variable, the FAO proposed to use the Hargreaves equation as an alternative to estimate ET0 , but the Hargreaves equation may require local calibration prior to its application. In this study, the meteorological data from 1951 to 1999 of the 24 weather stations in Ningxia was used for calculating ET0 by the Penman - Monteith equation and Hargreaves equation respectively.Then, the empirical coefficient of the Hargreaves equation were determined by regression analysis for different regions which are represented by meteorological stations; And then, modified Hargreaves equation was proposed and verified by using of meteorological data of each station from 2000 -2012. Results showed that： （ 1 ） The performance of the original Hargreaves equation in Ningxia is poor; it is much different from the results calculated by Penman - Monteith equation. （2） The accuracy of the modified Hargreaves equation is significantly improved, in good agreement with the results by the Penman - Monteith equation. Thus using the modified Hargreaves equation as an alternative to estimate ET0 is feasible in Ningxia.